diff --git a/include/services/gtsi_svc.h b/include/services/gtsi_svc.h
index cb942ed..ef4289f 100644
--- a/include/services/gtsi_svc.h
+++ b/include/services/gtsi_svc.h
@@ -14,12 +14,16 @@
 #define GTSI_ERROR_INVALID_PAS		-3
 
 /* The macros below are used to identify GTSI calls from the SMC function ID */
-#define GTSI_FNUM_MIN_VALUE	U(0x100)
-#define GTSI_FNUM_MAX_VALUE	U(0x101)
+#define GTSI_FNUM_MIN_VALUE	U(0x1B0)
+#define GTSI_FNUM_MAX_VALUE	U(0x1B1)
 #define is_gtsi_fid(fid) __extension__ ({		\
 	__typeof__(fid) _fid = (fid);			\
 	((GET_SMC_NUM(_fid) >= GTSI_FNUM_MIN_VALUE) &&	\
-	 (GET_SMC_NUM(_fid) <= GTSI_FNUM_MAX_VALUE)); })
+	(GET_SMC_NUM(_fid) <= GTSI_FNUM_MAX_VALUE)  &&	\
+	(GET_SMC_TYPE(_fid) == SMC_TYPE_FAST)	    &&	\
+	(GET_SMC_CC(_fid) == SMC_64)                &&	\
+	(GET_SMC_OEN(_fid) == OEN_STD_START)        &&	\
+	((_fid & 0x00FE0000) == 0U)); })
 
 /* Get GTSI fastcall std FID from function number */
 #define GTSI_FID(smc_cc, func_num)			\
@@ -28,8 +32,8 @@
 	 (OEN_STD_START << FUNCID_OEN_SHIFT)	|	\
 	 ((func_num) << FUNCID_NUM_SHIFT))
 
-#define GRAN_TRANS_TO_REALM_FNUM	U(0x100)
-#define GRAN_TRANS_TO_NS_FNUM		U(0x101)
+#define GRAN_TRANS_TO_REALM_FNUM	U(0x1B0)
+#define GRAN_TRANS_TO_NS_FNUM		U(0x1B1)
 
 #define SMC_ASC_MARK_REALM	GTSI_FID(SMC_64, GRAN_TRANS_TO_REALM_FNUM)
 #define SMC_ASC_MARK_NONSECURE	GTSI_FID(SMC_64, GRAN_TRANS_TO_NS_FNUM)